1. Field of Invention
The present invention relates to improved fuel cell assemblies for generating electric power, and more particularly to a method for providing combined sealing media between individual fuel cell plates and insulation between fuel cell units, all in a single process.
2. Description of the Prior Art
It is known to apply resilient sealing beads to and between the faces of fuel cell plates for controlling fluid flows between pluralities of such plates, stacked in pairs and bolted together for generating electric power. In a typical fuel cell stack arrangement, the pluralities of such plates are sandwiched together in a parallel, face-to-face pattern. The plates are held spaced apart by resilient sealing beads typically adhesively bonded to the face of at least one of any two adjoining plates. The sealing beads fit within grooves on the faces of the plates, and define paths or channels for fluids to flow between the plates. Normally, the fluids include not only fluid electrolytes used for generation of energy, but also coolants as will be appreciated by those skilled in the art.
The cell plates employed in the usual fuel cell are normally formed of plastic composites that include graphite. The sealing beads are formed of an elastomeric material. The beads are normally adhesively applied to the plates by a bonding agent, although in some cases the beads are simply held in place by pressure of compression created by bolted connections between plates. Each fuel cell unit is comprised of a cathode and an anode plate. Between each cathode and anode plate of each cell flows a coolant material of either a glycol-based anti-freeze or deionized water. Between each cell unit flows two chemically reactive elements, hydrogen and oxygen, separated by a catalytic membrane. The hydrogen and oxygen elements react at the membrane to form water vapor in a type of reverse electrolysis.
The nature of the chemical reaction, along with a need for separation of the coolant from the reacting elements, occasionally requires that extreme or costly measures be taken to avoid leakage through or between the plates. Thus, an improved mechanism is needed to assure against leakage between adjacent fuel cell plates, one that is highly reliable, particularly in mass production manufacturing environments.
A fuel cell apparatus includes a plurality of individual fuel cell units, each including at least two facing, parallel plates, mated together. A resilient sealing media, preferably formed of an elastomeric material, is employed to seal the plates together. The sealing media may be applied in the form of a curable fluid sealing material, which after being cured in place, is adapted to facilitate control of fluid flows, such as coolants between the plates, and of electrolyte flows between fuel cells. Upon completion of manufacture, a plurality of such parallel, stacked plates that incorporate the present invention are separated by a plurality of discrete resilient sealing beads disposed over selective portions of the surfaces of the two facing plates.
Specifically, the invention involves the manufacture of fuel cell units, each unit defined by a pair of plates comprising an anode and a cathode plate, in which the cathode plate and the anode plate are sealingly bonded together. Pluralities of such fuel cell units are stacked and secured together to form commercially available composite fuel cell structures utilized to generate electric power, either domestically (i.e. for home use) or for use in vehicles.
The invention offers a combination sealing and insulation procedure in which pairs of such fuel cell plates may be manufactured in a simple and efficient manner. The method employed involves the injection of a rapidly curable liquid silicone into an aligned mold aperture of one of the mated plates, whereby liquid silicone may flow via the apertures through the other plate, as well as between the plates in order to establish a seal between cathode and anode plates. Moreover, the liquid silicone is injected into aligned mold gating apertures of the cathode and anode plates, flows entirely through both plates, and forms an insulation layer on the backside of the bottom plate. In the preferred embodiment described herein, the bottom plate is the anode.